Nitride semiconductors have received considerable attention for use in the development of light emitting diodes, ultraviolet diodes, photodetectors and high power, high voltage, and high temperature transistors. In the 1990's, two breakthroughs were made in nitride semiconductor growth: the fabrication of high-quality aluminum gallium nitride (AlGaN) films and the realization of p-type GaN. Following these, blue and green light emitting diodes (LEDs) and laser diodes have been commercialized, and ultraviolet (UV) LEDs began to be reported based on AlN.
The AlGaN films are typically grown by industrial scale metallo organic chemical vapor deposition (MOCVD) techniques. To achieve acceptable quality of the films, the growth is performed with a high precursor flow, such as NH3 and TMG (trimethylgallium) or TMA (trimethylaluminium), and hence high partial pressures. A commonly used measure is the so called “V/III ratio” which relates the molar flow of the precursor elements for the group V and group III elements, for example the molar ratio between the NH3 and TMG.
Recently, 1-dimensional nano- and micro-structures that are nanowires fabricated based on nitrides have attracted plenty of attentions from researchers. Several methods, such as VLS, template-confinement growth, and oxide-assisted growth, have been reported for growing AlGaN nanowires. In addition, selective area growth of AlGaN has also been studied extensively to reduce the dislocations density in AlGaN films based on nanowires. These structures offer many benefits for light emitting devices. They allow for reduction of dislocation densities within structures, can lead to devices with improved light extraction efficiency and temperature management.